The Gatekeeper's Son (The Gatekeeper's Son #1) by C.R. Fladmark

Junya’s grandfather is a billionaire who keeps the secret to his success hidden in a heavily guarded safe.
His mother is a martial artist who wields a razor-sharp katana—and seems to read his mind.
And a mysterious girl in a Japanese school uniform can knock him over—literally—with just a look.
What do they know that he doesn’t?
Junya’s life takes a dangerous turn on his sixteenth birthday, when someone sets out to destroy not only the family’s business empire—the one that he’s set to inherit—but Junya himself. He’s fighting for his life, and doesn’t know who to trust.
What has his family been keeping from him?
Junya’s journey takes him from the narrow streets of San Francisco to Japan, and through hidden portals to the top of the ancient Japanese Izumo Shinto shrine, to places where death and violence are a way of life. And in a mystical world he’s never imagined, he finds his true destiny.
Kindle Edition, 313 pages
Published October 1st 2014 by The Shokunin Publishing Company 
Junya has several events that happen just after he turns 16. A young Japanese girl keeps appearing in his life, he is told he is the heir to his grandfather's estate/business and the awakening of his powers. 
Junya was my favorite character as he tries to figure out everything that has come his way in only a matter of hours. His reactions to the things that happen around him are realistic, but the world and adventures are fantastical. There were some characters like grandfather and Shoko that left me hanging their actions at times felt very random and the scenes with them a bit choppy. Yet Junya takes it all in stride and rolls with it. 
The only normal relationship Junya has is with his best friend. All the interactions between him and his grandfather, parents and Shoko involve this otherworldly fantasy relationships. This has a lot to do with all of the secrets that have been kept from him. As he is trying to figure things out, crazy and unusual things happen all around him and includes everybody he knows. 
If this story were shortened and made into a manga or comic the parts I felt a little choppy in the story would in my opinion make more sense. I did feel that the book was a bit long for the story that was being told and would work better as separate sections or novellas or as a comic. 
The ending of the book was a good ending. Junya really shows a lot of growth and strength from his experiences and it ends strongly. It is something I would recommend to those that enjoy Manga and looking for a story form of that.